We examined the thermal structure of the crust across complex deformation zones in SW Turkey using the Curie Point Depth (CPD) estimates and made comparisons of the thermal state of the crust with the seismic activity to provide insights for spatial limits of brittle failure in this region. The CPD estimates of SW Turkey from 80 overlapping blocks vary from 9 to 20 km. SW Turkey has two regions of shallow CPD. The shallow CPD region in the Usak-Afyon zone in western part of the study area is caused by upper crustal thinning and shallowing of high conductivity lower crust. The other shallow CPD region is in the Central Anatolian Volcanic Province in the eastern part of the study area and is thought to be related to the presence of silicate melts in the shallow-level crust. A NNW-SSE trending belt of deep CPD region separates these two zones and is located along the boundary of high (west) and low (east) seismic activities. It is interpreted that the regional thermal structure in SW Turkey is mainly controlled by the processes associated with the African-Eurasian plate convergence zone. The N-S lithospheric extension above the subducting slab created a thermal dome in Western Anatolia in response to upwelling of asthenosphere. Post-collisional magmatism of Neogene-Quaternary age generated another thermal dome in the eastern area. Comparison of the CPD variations with the seismic activity has shown that large earthquakes occur near the margins of the inferred regional thermal domes. Low seismic activity within the regionally active seismic areas seems to be associated with shallow CPD and high heat flow.

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We compare, for the first time, geomagnetically-conjugate plasma bubbles observed by ground-based OI 630.0-nm all-sky imagers at Shigaraki, Japan (34.8°N, 136.1°E; magnetic latitude 25.4°N) and Darwin, Australia (12.4°S, 131.0°E; magnetic latitude 22.0°S), with global-scale plasma structures (-10, 000 km in longitude) in the equatorial anomaly simultaneously detected with an OI 135.6-nm imager on the IMAGE satellite at -7 earth radii. As found previously, global-scale plasma structures in both hemisphere imaged by IMAGE consist of an array of geomagnetically-conjugate small- to medium-scale (a few hundreds to 1000 km in longitude) wavy structures that move to the east at -100 ms^-1. We find the following: 1) plasma bubbles detected with the all-sky imagers reach an apex altitude of -1800 km over the geomagnetic equator while moving to the east at -100 ms^-1 with spacings of 200-250 km. 2) Bubbles observed with the all-sky imagers and IMAGE are embedded within the small- to medium-scale wavy structures, and some of them are located near the crest of an enhanced electron density region associated with the wavy structures. 3) The bubbles and wavy structures that are generated near sunset slant to the west with increasing latitude in both hemispheres, and tilts do not change with longitude (i.e., local time). The results suggest that the generation and evolution of plasma bubbles are closely related to those of the small- to medium-scale plasma structures.

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Winds measured by an all-sky meteor radar have been used to investigate the terdiurnal tide in the mesosphere and lower thermosphere (MLT) region overWuhan (30.6°N, 114.4°E). We present a climatology of the terdiurnal tide at low-mid latitude site during the period of April 2002 to December 2004. The terdiurnal peak is distinct in the long-term power spectrum of the wind. The monthly and seasonal mean maximum amplitudes have values of 7 m/s and 5 m/s, respectively. The short-term amplitudes can occasionally reach up to 30 m/s, and at times the terdiurnal tide is as large as the diurnal and semidiurnal ones. It seems that the meridional component is more regular than the zonal one. An obvious annual variation is observed in the meridional phases with a phase leading in winter than that in summer. The annual variation for the terdiurnal tidal amplitude is not obvious, and is variable from year to year in our observations. This seasonal trend is slightly different from earlier studies at other locations.

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The formation of Al₂O₃ phases by the solid-solid reaction of a metallic Al layer evaporated on a SiO₂ amorphous grain has been induced by heating above 600°C in vacuum (1×10^-6 Pa). The distortion process of the amorphous SiO₂ grains by the formation of Al₂O₃ have been directly imaged by in-situ TEM observation. A partly deposited Al layer covered the SiO₂ grains after heating at 750°C, and γ-Al₂O₃ grains of about 25 nm diameters were formed on the SiO₂ surface. Upon the growth of Al₂O₃, the SiO₂ grain decomposed into a mixture of metallic Si and SiO₂ and disappeared as a result of sublimation due to the formation of SiO_x at high temperatures. The present result on dust surface dynamics will become an important field with respect to the metamorphism of grains from the astromineralogical viewpoint.

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Using seismograms recorded at 582 Hi-net stations for earthquakes located within 30 km from each station, we measured coda Q for frequency bands of 1-2, 2-4, 4-8, 8-16, and 16-32 Hz, respectively. Then coda Q maps are constructed with average station spacing of 20 km over Japan, except the Hokkaido Island. The most striking feature of the obtained maps is the significant spatial variation within Japan, up to a factor of 3 for the lower frequency bands, as well as its strong frequency dependence. Such high spatial resolution was not possible to achieve without the high density and sensitivity of the Hi-net. We found several low coda Q regions for frequency band of 1-2 Hz including the southwestern Shikoku, eastern Shimane-western Tottori along the Japan Sea coast and the disjointed spots along the Pacific coast from the Kanto-Tokai region to southern edge of the Kii-peninsula. However, the most conspicuous low coda Q zone is a narrow belt from Niigata towards south-west to the Biwa lake along the Japan Sea coast. This low Q zone appears at frequency bands of both 1-2 and 2-4 Hz, and it coincides with the zone of high deformation rate revealed from the GPS data. For frequency bands 4-16 Hz (2-4 Hz in Kyushu), the low coda Q areas agree with volcanic and geothermal areas. For frequency band of 16-32 Hz, the coda Q is distributed nearly uniformly throughout the study area.

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A shallow destructive inland earthquake of M6.8 occurred on Oct. 23, 2004 (JST) in the middle part of Niigata prefecture, Japan. The aftershock activity was high as compared to those of the other shallow inland earthquakes in Japan. We relocated the sources of the main shock and aftershock activity by adopting the double-difference earthquake location algorithm. The precisely relocated hypocenter distribution shows that there are a doubleplanar structure with a distance 5 km in parallel dipping in WNW with about 50 degrees and a single-planar structure dipping in ESE with about 15 degrees. The upper and lower planes of the double plane began to be formed with the main shock and the largest aftershock of M6.5, respectively, while the ESE dipping plane began to be formed with the 3rd largest aftershock of M6.1. The three planes represent the fault planes of the large events mentioned above. The aftershock distribution is found to be a superposition of the fault planes of the main shock and the large aftershocks. The high aftershock activity is attributed to the formation of the fault planes.

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A seismic network was deployed the day after the main shock of the 2004 Mid-Niigata Prefecture Earthquake to determine the major source faults responsible for the main shock and large aftershocks. Using the high-resolution seismic data for five days, three major source faults were identified: two parallel faults dipping steeply to the west located 5 km apart, and another dipping eastward and oriented perpendicular to the west-dipping faults. Strong lateral changes in the velocity of the source area resulted in the locations of the epicenters determined in this study being located approximately 4.3 km west-north-west of those reported by the JMA routine catalogue. The strong heterogeneity of the crust is related to the complex geological and tectonic evolution of the area and therefore the relatively large aftershocks followed around the main shock. This is considered to be responsible for the prominent aftershock activity following the 2004 Niigata event.

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Crustal deformation associated with the Mid Niigata prefecture Earthquake in 2004 (M_JMA = 6.8) was detected using RADARSAT SAR interferometry. A displacement of -40 cm in the line-of-sight to the satellite was observed to the west of the main shock epicenter, and a displacement of 20 cm was observed to the east of the epicenter. Fault parameters estimated from the obtained deformation were in good agreement with those of the Centroid Moment Tensor solution for the main shock provided by the Japan Meteorological Agency. In the postseismic period, a steep gradient of deformation was found around the Obiro and the Western Muikamachi Basin faults, indicating that a fault-slip occurred in the shallow part of the fault. Since the seismicity in the shallow part of the Western Muikamachi Basin fault was very low, we believe that it must have been an aseismic slip. Crustal deformation associated with an aftershock that occurred on October 27 (M_JMA = 6.1) was detected, and it was ascertained that this aftershock had ruptured the conjugate plane with respect to the Obiro fault. Since locations and/or mechanisms of these faults differed significantly, it was determined that at least three faults were involved in this series of earthquakes.

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The 2004 mid Niigata prefecture earthquake with M6.8 occurred in the north of central part of Japan. It was a reverse fault by the regional compression stress field in NW-SE direction. Several aftershocks with M≥6 were occurred. The large aftershocks occurred on plural fault planes. The plane was either parallel or normal to the main shock one. We estimated three dimensional velocity structures in and around the focal area of the earthquake by using a Double Difference tomography method. The arrival time data were picked from seismograms at the deployed seismic stations settled by Kyoto and Kyushu universities in collaboration, NIED, ERI, and JMA. The velocity structure showed that a low velocity zone existed in the northwest part of the aftershock area. On the contrary, the velocity in the southeast became high. Moreover, the fault plane of the main shock inferred from the aftershock distribution was located at the velocity boundary.

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A destructive large earthquake (the 2004 mid Niigata prefecture earthquake) sequence occurred in the central part (Chuetsu district) of Niigata prefecture, central Japan on October 23, 2004. We have deployed a temporary seismic network composed of 54 stations for aftershock observation just above and around the focal area of the earthquake for about a month. Using travel time data from the temporary seismic network and surrounding routine stations, we obtained precise aftershock distribution and 3D seismic velocity structure in and around the fault planes of the earthquake and four major (M ≥ 6) aftershocks by double-difference tomography. The results clearly show three major aftershock alignments. Two of them are almost parallel and dipping toward the WNW. The shallow and deep aftershock alignments correspond to the fault plane of the mainshock and that of the largest aftershock (M6.4), respectively. The third alignment is almost perpendicular to the WNW-ward dipping planes and perhaps corresponds to the fault plane of the M6 aftershock on October 27. General feature of the obtained velocity structure is that the hanging wall (western part of the focal area) has lower velocity and the footwall (eastern part of the focal area) has higher velocity. Major velocity boundary seems to shift westward in comparison to in northern and southern parts at a location near the central part of the focal area, where the main shock rupture started. Some parts of the fault planes were imaged as low velocity zones. This complex crustal structure would be one of possible causes of the multi-fault rupture of the 2004 mid Niigata prefecture earthquake sequence.

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Across the source region of the 2004 Mid-Niigata Prefecture earthquake, wideband magnetotelluric (MT) survey was performed just after the onset of the mainshock. Owing to the temporal stop of the DC powered railways around the area together with intense geomagnetic activity, we obtain MT records with excellent quality for both short and long period data, as long as 10, 000 s. Two dimensional regional strike is evaluated with the aid of the Groom-Bailey tensor decomposition together with induction vector analysis. As a result, N15°W is determined for the strike. This strike is oblique to the local geological trend and also to the strike of the main shock source fault together with aftershock distribution of N35°E. Two dimensional resistivity structure is determined with the aid of an ABIC inversion code, where static shift is considered and estimated. Characteristics of the structure are as follows. (1) About 10 km thick sedimentary layer exists on the top. (2) A conductive body exists in the lower crust beneath the source region. The mainshock occurred at the boundary of the conductive sedimentary layer and a resistive basement beneath it and aftershocks occurred in the sedimentary layer. From geological studies, it is reported that the sedimentary layer was formed in the extensional rift-structure from Miocene to Pleistocene and has been thickened by compressional tectonic regime in the late Quaternary. Interstitial fluids or clay minerals, which reduce the sedimentary layer resistivity, control the reactivation of the normal fault as the mainshock thrust fault and aftershock activity. The second conductive body probably indicates existence of fluids in the depths as well. Such a conductive layer in the lower crust was also revealed by previous MT experiments along the Niigata-Kobe Tectonic Zone and probably plays a main role in concentration of strain rate along the zone.

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The Mid-Niigata Prefecture earthquake in 2004 (M_JMA 6.8) generated surface ruptures along the eastern rim of the Uonuma Hills. To elucidate the structural linkage between the surface ruptures and the source fault at depth, the high-resolution seismic reflection profile across the surface ruptures and nearby active faults, and the data of aftershock distribution are examined. The 5.2-km-long, high-resolution, depth-converted seismic section reveals an emergent thrust beneath the surface ruptures. A two-dimensional model of the fault geometry has been constructed based on the aftershock distribution and the shallow reflection profile. The development of the main geologic structure are well explained by forward modeling using a balanced cross-section method. In detail, the fault system generated the main shock dips at a steep angle (60°) below 5 km depth and more shallowly (30°) near the surface.

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The geologic structure of the Uonuma Hills, the site of the 2004 Mid-Niigata Prefecture Earthquake (M_JMA 6.8), Japan, is examined based on published geologic maps, drill hole data and seismic reflection profiles. The Uonuma Hills are located in an active folding area on the eastern margin of the Niigata sedimentary basin, and are divided into three discrete regions from north to south based on the geologic structure. The southern extent is marked by a west-dipping homoclinal structure produced by reverse faulting of the west-dipping Muikamachi active fault. The central section exhibits a regional anticlinorium produced by west-dipping reverse faulting with a steep angle at depth (> 5 km) and a more shallow angle (30°) near the surface. This fault can be correlated with the source fault responsible for the main shock. The Muikamachi fault consists of two fault segments and the source faults of the northern and the southern segments show discrete geometry forming an step over. Thus, judging from the geologic structure, the 2004 Mid-Niigata Prefecture Earthquake ruptured to the maximum possible extent in this fault segment in the central part. Furthermore, this study reveals that the activity on the Muikamachi fault, which has an apparently continuous surface trace, is produced by two different source faults at depth, with important implications for seismic risk assessment.

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We present a novel mechanical model for the extraction of outer core material upwards across the CMB into the mantle side region of D″ and subsequent interaction with the post-perovskite (ppv) phase transition. A strong requirement of the model is that the D″ region behaves as a poro-viscoelastic granular material with dilatant properties. Using new ab-initio estimates of the ppv shear modulus, we show how shear-enhanced dilation promoted by downwelling mantle sets up an instability that drives local fluid flow. If loading rates locally exceed c. 10^-12 s^-1, calculated core metal upwelling rates are >10^-4 m/s, far in excess of previous estimates based on static percolation or capillary flow. Associated mass flux rates are sufficient to deliver 0.5% outer core mass to D″in < 10⁶ yr, provided the minimum required loading rate is maintained. Core metal transported upwards into D″may cause local rapid changes in electrical and thermal conductivity and rheology that if preserved, may account for some of the observed small wavelength heterogeneties (e.g. PKP scattering) there.

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Deep-tow vector magnetic data have been acquired across the fast-spreading southern East Pacific Rise 18°S and inverted to magnetization intensity variations. Vector magnetic data are used to determine continuous magnetic intensity within intervals of constant polarity over the Matuyama and Brunhes periods up to the Cobb Mountain event at 1.19 Ma. A comparison of our deep-tow vector data and a sediment core-derived geomagnetic paleointensity timescale suggests that the short-wavelength magnetic anomaly signal is indeed of geomagnetic origin and can be used to date the seafloor with a high resolution. The crustal age determined from our date reveals a highly asymmetric spreading rate for the recent period (since 0.3 Ma).

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